Hot brakes , how do they feel?Is this a symptom?

[z12358]

One more thing, Porsche track experts from the club recommend changing your brake fluid at least once a year if you do more than a couple of track events a year. I plan to do it every year.

Jim, is it better to do brake fluid change before winter storage (just like oil) or after?

Z.

[986 Girl]

Found a pretty helpful site for those of us who have never bled or flushed brakes before...thought someone else might find this handy.

http://www.bombaydigital.com/boxster/projects/brakes/bleed_and_flush/

There are a couple other walkthroughs on there (changing rotors, pads, etc) and most sections have a ton of helpful pictures.

[MNBoxster]

Originally Posted by z12358

One more thing, Porsche track experts from the club recommend changing your brake fluid at least once a year if you do more than a couple of track events a year. I plan to do it every year.

Jim, is it better to do brake fluid change before winter storage (just like oil) or after?

Z.

Hi,

It's a toss up - Change it in the Fall to prevent any built up moisture from attacking your Braking System, or change it in the Spring so you have the lowest possible moisture content through the Driving Season.

Personally, I do it in the Spring to gain maximum benefit from the Fluid for driving. Corrosion will shorten your Braking Systems life, but probably not too badly if you habitually change it every year...

Happy Motoring!... Jim'99

[MNBoxster]

Hi,

@CJ_Boxster - Some systems are vented while others are not, with Modern ABS Systems, vented Reservoirs are being seen less and less. But, even the sealed systems can/do allow some air (along with it's moisture) to pass the Cap Seal - it's not a perfect seal.

I am totally familiar with the inner workings of a Master Cylinder and have certainly rebuilt many more than you have racked up years - not dissing you, just making an example, in fact I rebuilt a Girling MC for a friend of mine last weekend.

According to the SAE DOT 4 Brake Fluid absorbs between 1.5-2% moisture by weight annually, even in a sealed system. This is because the primary source of moisture invasion comes from the Flexible Brake Hoses at the Calipers and past the Piston Seals themselves. Fluid cannot pass, but minute amounts of moisture can.

Consequently, every 2 years the average system will contain about 4% moisture by weight and should be changed. This much moisture may not dangerously affect the Wet Boiling Point (though it may for some fluids), but 4% Moisture will attack the system components. Also, the SAE found that the moisture content was not linear throughout the system but was found in higher concentrations in the Calipers (because they are closer to the Flexible Hoses and Piston seals), while the Fluid in the Reservoir may have a lower moisture content. They use a Refractor to determine the Moisture content sampled from different parts of the system.

And, the worst place to experience Fluid Boil is in the Calipers because their effectiveness can be reduced to nothing as some people here have found...

Happy Motoring!... Jim'99

[CJ_Boxster]

interesting, I had no idea that some abs systems were vented. Thanks.

[edevlin]

This is somewhat off topic, but does relate to braking. I was wondering if one should push in the clutch when doing hard braking from higher RMP's. It seems like if you dont, you are applying breaks to not only the wheels but the engine as well.

Ed

[MNBoxster]

Originally Posted by edevlin

This is somewhat off topic, but does relate to braking. I was wondering if one should push in the clutch when doing hard braking from higher RMP's. It seems like if you dont, you are applying breaks to not only the wheels but the engine as well.

Ed

Hi,

You would normally want the engine to do some of the braking, at least initially. But, I am not a fan of downshifting for normal driving, just let the engine wind down in the gear it's in until the Revs drop and then shift to neutral and let the Brakes do all the work. This is because of excess wear to the Clutch and Drivetrain.

Let's assume that your Clutch has only so many shifts in it. Using them for Downshifting to stop uses a lot of these available shifts for Braking, not driving. Plus, engaging the Clutch when the car still posesses a lot of inertia, places a strain on the Clutch, Synchros, Tranny and Axle Shafts, CV Joints, and the like, shortening their Service Life.

Brake pads are cheap - $150-$200, while the Clutch is $400-$1,000. As soon as you've bled off a lot of the inertia in the gear you're in, say 10-20 MPH, shift to neutral and use the Brakes until the car comes to a stop. Downshifting is unecessary, except to please the ears or impress that young Philly at the Stoplight. Both important, but at the cost of replacing components before you'd otherwise need to.

Of course, all this goes out the window in an Emergency. In this case, do everything you can to stop in as short a distance as possible - Downshift, Brake, even throw out a Boat Anchor if you have one.

But, in normal driving, you'll extend the life of your Drivetrain if you adopt the practice I've outlined above. Anticipate your stops, let Gravity reduce your inertia as much as possible and add the Brakes to bleed off the final amount of energy til you come to a full stop...

Happy Motoring!... Jim'99

[Dohertycm]

If you brakes are getting hot, it could be a couple of things. And there are a couple of things you can do to prevent it or reduce it.

First you could have moisture in your brake fluid, and when your brake fluid gets hot the water will boil off and create air in your lines which is why the brakes fade, because the air is being compressed. So you would need to change out your brake fluid. The rule is once a year...and you would be surprised what kind of crap builds up after only a year... And go with a good racing brake fluid.

Second, what type of pads are you using..Metal Masters will heat up quickly. I personally use Hawk racing pads on my 911 on the track, I have yet to get a brake fade. They disapate heat really well. So the quality of Brake pads is a factor as well.
These are two main areas where you will need to start. If you get brake fade after these are corrected, then you need to look at your driving habits...

Chris